Telephone system



1927' c. E. LOMAX TELEPHONE SYSTEM Original Filed May 16. 1921 3 Sheets-Sheet -Inuan 13F?- L'larsnua ELnmax W C. E. LOMAX TELEPHONE SYSTEM Sept. 6, 1927.

nuen 1:1 Elaramza Elumax e t. S p 1927 c. E. LOMAX TELEPHONE SYSTEM 5 Sheets-Shet 3 Him- Elarannafil Ema w Patented Sept 16, 1927.

1,641,931 PATENTp-OFFI'CE.

CLARENCE E. LOMAX, OF CHICAGO ILLIN'OIS,ASSIGI TOR, BY ,I VIESIT E ASSIGNMENTS, '10

AUTOMATIC ELECTRIC .INC., 0F CLI-IICJAGO, ILLINOIS, A CORPORATION 'OF DELA- WARE; I

TELEPHONE, SYSTEM.

Application filed May 16, 192 1,Seria 1; No. 469,909. RenewedJ'anuary 5, 1927.

1 The present invention relates in general to telephone systems, but morefv especially to private branch exchange systems, and in particular to a type of branch exchange which is adapted for use by the fire and police departments of "a large city. In such systems the servicerequirements are very exacting, and a combination automatic and manual branch exchange 'system has been designed, therefore, with a to providing a system of maximum reliability, which at the same time takescare or all the different operating requirements.

The various jteatures" of the invention will be pointed out and described hereinafter with reference to the accompanying drawings, comprising Figs. 1, 2, and 3, which show by means of'theusual circuit diagrams a fire andpolice systemembodying the principles of the invention;

' Referring to the drawing," the lsystem' therein depicted is a 100 line branch exchange which is interconnected with-a manual main exchange by agroup of trunk lines;

In Fig. lone of these interconnecting trun' k lines, comprising conductors 20 and 21, is shown extending from the jack J'ln the main exchange to theplug ending cord cir- ,cuit O in the branchjexc'han e; The main exchange equipment is old and only enough ofi't is shown to enable the operation to be ei'ence character 0". "This cord circuit is used ,"for completing local connections when the branchfexchange s being operated'as a manual'eXch an-ge,

station of the' usual type-and is provided with a calling device for controllingthe automaticiswitcheswhen' the system is operasan automatic system. The line convductors 101i and 'l02extend through contacts in the relay e'uipment'associated with the inultiple' jack g lt, by way of conductors 110 and .112 to the relay equipment associated with the answering jack J7, and thence through certain contact'springs toline con- The subscribers individual line switches,

such as the line switch C, Fig. 2, have access ;.to a group 'ot' trunk lines terminating in the local connectors, which are ofthe well known Strowger vertical and rotary. type. One

of these trunk lines is shownin'thed-ra-wing and comprises conductors 158, 159, and

160, whichextendto and terminate in the local connector H, Fig. 3. This local con- ,nector; is of the connector selector repeater type, by which-is meant a connector switch which'on certain levels operates as an ordinary connector for completing local connections, while on another level, known as the trunking level, it operates as a selector to automatically select an idle trun'k line. When operating on this trunking level when amal am-n1; line is selected, the circuits in the'connector are altered so as to complete a bridge across the selected trunk line. The

serves to actuate asign'al at thefdistant manual exchange, and since the bridge is under closure of the-bridge across the trunk line the control of theline relay of the localconp v nector if the'main exchange is of the auto-' explained. The cord circuit 0, it wrl'l be matic'type, instead of the manual ;type, the

local connector is now adaptedto operate as a repeater to control automatic switches in the main exchange. Hence the name connector selectorrepeatera 1 1 As stated hereinbefore, the branch exchange system may be operated either as an automatic system oras a manual system.

With this key in-its normal position, as shown in the drawing, the'system' is adapted The position of the key K? in Fig. 2 is what v 1 determines the character of the system. I, In 2011c of the local-stations is shown and is indicated by the reference character 4A; The substation A is an automatic sub for automatic operation, while it the key is m actuated and lett-"in operated position the automatic equipment is removed from the control ofthecalling subscribers and. the system, will operate as a manual system.

For convenience in describing'the various features of the invention, which will now be proceeded with, it will be assumed first that the's'ystem is operating automatically,

1 The process of establishing a local connection will first be; explainedand for this purpose it will be assumed that the subscriber at substation A, Fig. 2, wishes to obtain connection with the subscriber at substation A, Fig. 3. lVhen the receiver is removed a. circuit is completed for the line relay 1 of the individual line switch C and for the line relay 115 associated with the answering jack J which may be traced as follows: from ground at the individual line switch C by way of cut oil springs 146 and 145. conductor 180, resting contact of armature 120 and the said armature, conductor 110, resting contact of armature 107 and the said armature, line conductor 101, the calling device, transmitter and receiver at substation A, line conductor 102, armature 109 and its resting contact, conductor 112, armature 122 and its resting contact, conductor 133, cut oil springs 14:3 and 11 1 and through the windings of relays lit) and 115 in parallel to battery. Upon the closure of the foregoing circuit, relays 1 10 and 115 are both energized and the former relay upon attracting its armature closes a circuit for the pull down winding lll of the line switch C. The pull down winding is at once energized and operates both the cut oil armature 1 1? and the plunger arm 148, the former being ellective to separate the cut off springs 1 13 and 1 15 from springs 14: 1 and 1 10, respectively, while the latter is effective to force the bank springs 150, 151, 152, and 153 into engagement with bank contacts 15 1, 155, 156, and 157, respectively. By the separation of the cut'oll' springs the energizing circuit for line relays 1&0 and 115 is broken, and relay 115 at once falls back. Relay 1 10, however, is slow acting and retains its armature attracted for a brief interval, long enough for a holding circuit to be established at the connector H, as will be described. By the engagement of bank springs 150 and 153 with bank contacts 154- and 157 the calling line is extended by way of trunk conductors 158 and 160 to the line relay 200 of the connector H, and the said line relay is at once energized over the calling subscribers line circuit. On attracting its armature 217, relay 200 closes a circuit for the slow acting release relay 201. which upon energizing prepares the switch for its vertical operation at armature 218 and at armature 219 connects ground to the release trunk conductor 159. By the latter operation, a holding circuit for the line switch C is completed which extends b way of the now grounded armature 219 of relay 201, release trunk conductor 159, bank contact 155, bank spring 151 and through the holding winding 142 of the line switch C to battery. The energization of the holding winding 1 12 serves to maintain the cut oil armature 14:7 and the plunger arm 118 in operated position. A branch of the holding circuit extends by way of conductor 131 and armature 121 and its resting contact to the winding oi relay 116 associated with the answering jack J, and this relay is accordingly energized to open the circuit of relay 117. Another branch extends by way of conductors 131 and 111 and armature 108 and its resting contact to relay 10 1 which is associated with the multiple jack J Relay 10daccordingly energizes and opens the circuit ol relay 105. By the energization of relay 110 and 101 the operator or operators are prevented from listening in on the call, or from interfering with it in any way whatsoever. .In order to notify the operators that the line is in use, the busy lamps L and U are provided which are connected with conductors 131 and 111, respectively, and which are, therefore, lighted at this time. There is still another branch of the holding circuit which extends by way of conductor 181 to test contact 26a and its multiples in the banks of the local connector switches. where by a ground potential on these test contacts the line of substation A is made busy. The operation of the line switch Cl is, 01? course, :l'ollowed immediately by the operation of the master switch MS. When the bank spring 152 on gages bank contact 156 ground is placed on conductor 101 extending to a contact in the master switch bank and a circuit is co1npleted :tor the starting relay 1.63. Upon energizing, the latter relay closes a circuit for the locking magnet 16 1. Upon energizing, the locking magnet unlocks the master switch shaft and closes a circuit for the motor magnet in order to advance the shaft and re-align the plungers oi the idle line switches in front of an idle trunk line, while at the same time the open main conductor 102 is disconnected from the negative pole of the battery in order to prevent the operation of any line switch while the master switch is in operation.

The calling line has now been extended through to the connector H, which is ready for the reception of impulses produced by the calling device at the calling station. hen the calling device is operated in accordance with the first digit in the number at substation A, a series of interruptions is produced in the circuit of the line relay 200 and the line relay accordingly deener; gizes a like plurality of times, scndingat each deenergization an impulse of current through the vertical magnet over the following path: from the grounded arn'lature 217 by way of the resting contact oil-f said armature, armature 218 and its working contact, 00' normal springs 215 and 213, winding of the slow acting series relay 202 and the winding of the vertical magnet 210 to battery. 3y the operation of the vertical magnet the switch shaft is raised step by stop until the wipers 200, 261, and 262 stand opposite the horizontal level of bank conlit) merige's i tacts in which the line of substation A is 'termlnated. Relay 202 1s energized 1n series with the vertical magnet and being slow acting remains in operated position during the vertical operation of the switch. The operation of armature 221 of relay 202 or no consequence at this tiine but at armature 220 the vertical magnet circuit-is maintained closed notwithstanding the shifting ofthe otf normal springs which occurs at the first vertical step of the switch. At the end of the vertical operation relay 202 falls back and at its armature 220 transfers the "operating circuit to the rotary magnet 211.

said armature, armature 218, and its work" ing'contacaofi normal springs 2'15 and 21 i,

"armature 220 and its resting contact-f. norma cl'osed contact springs cont-rolled by armature 235, armature 242 and its resting contact andthe winding of the rotary magnet 211 to battery. By thesoperation 0L L116 rotarymagnet the switch shaft is rotated "step by step until the wipers 26 0, 261, and

262 are finally brought to rest in engagement with the particular set of bank con *sidered. at the present time At armature 7 235a relay connects te'st wiper 261 with file finding 0f t (test relay 206, while at ,{llllllllI-lllle 11 shunt, around he 'tactsjin which "thefline of substation A" is terminatec'l, these contacts being indicated in the drawing by reference numerals 266, 267, and 268. The slow acting relay 20v is energized in parallel with the rotary magnet and remains in operated position.

throughout the rotary movement of the switch. The circuit change produced by 'a mature 236 of relay 207 need not beconnormally closed contact controlled by arma 'ture 2330f relay 206, the latter operation' being eiiective to maintain therotary mag- {net circuit closed in case the test relay 206 should be operated by the engagement of test wiper 261 with grounded test contacts during'the rotation of the switch.-

Assuming first that the line of substation, A is busy when called when "thetest wiper 1261 comes to restlin engagement with test contact 26'? it will find a groundjpotential and the test relay 206 will be energized.

Upon energizing, the test relay opens the mrotary magnet circuit at armature 235,

opens the circuit of the switching relay 208 at the back contact of -armature234t, closes a locking circuit for itself at the working :contactoi't the -said armature 234', and at 7 us? al manner.

armature 233 connects a lead coming from the busy signalling machine to the lower side of the trunk line incoming to the connector switch. By this operation an and ible busy signal is transmitted to the calling subscriber, who is thus notified that the called line is engaged and isytherefore, inaccessible for the tune being.

Having described. 7 the operation which takes place when the called line is busy, it i will now be assumed that theline is idle when called. Under these when the test w per 261 comes to rest in engagement with test contact 267' it will find no ground potential and the test relay 206 Jill not'be energized. Then when the slow acting'relay 207 falls back an instant later a circuit is completed for the switching relay 208 which extends from the grounded reease trunk conductor159 by \vay'of armaure and its restingcont-act upper windactof armature 237 and the said armature, .,.rinally clo ed contact springs controlled .iy armature 24-0. test wiper 261, test contactconductor 291 and 't irough the holding no or substation A (not'shown) to V The holding winding295 is enerc and by operating the cut oil armature the line s *itcli clears'the line of its nor- 1 battery and ground connections in the It will be understood that the line equipment which is associated with the 'line of substation A" isthe same as the line equipment which is associated with substation iel, and since this line equipment is quite-complicated it has not been considered advisable to show itcomp'letely since to do so would involve ainere duplication of :Fig. '3 i 'f' llm I eis called-are shown however.

Rel-ays "in 2 and are ener ized to break the -ci"cuits of the relays corresponding to relays 11? and 105 in order to prevent the possiblh ity-of interference by the operator. It will be understood also that *the busy lamps which are associated withf-the called line are lighted in order to notify the operator that the line is in use. In the connector H, when switching relay 208 isenergized it establishes a locking circuit for itself at arrnature 2&1, opens the rotary 'magnet circuit at armature 242, connects ground 'to the test wiper 261 at armature 24:0, and at a r-matures 239 and2 l3 connects up the upper V and lower line wipers 2G0 and 262.- A 51 111211 circuit is now established over which at substation A and noti y the sub circumstances a; or the switching relay 208, resting c0nessential circuits .involved when the 2': correspond to relays 116 and rging current from the generator GEN is pro ected intermittently out over the called line in order to operate the bridged that he is war ed at'the telephone... Tlhe-upper windingctthe ring cutoff relay no oi the line switchyindividual 205 is included in the signalling circuit and when the called SllllSCllllQl answers by removing l is receiver relay 5305 it operated, establishing a lochiiui; circuit for itself at armature 231. in addition, relay it)? opens the signalling circuit at armalures 130 and 232 and at the working contains o'i these arnrutures linally completes the talking connec tion. Better the rinn cut-oil relay 205 is operated the hail; bridge relay or impedance coil rill?) is bridged across the called line in series with lhe hallery i1 order to supply talkingcurrent to the t ansniitler at the called station. The calling: station is, of course. supplied with talking; current through the windings of the line relay :200, and since the connection in now completed the subscribers may conrerse to ether as desired.

\Vhen the subscribers are through ta king, they will both replace their receivers. The release ol the connection brought about by the replzu'enmnt ol the receive at the calling station A. which arises the lini and release relays 20d and fil of the connector H to he deenern'ized. tln retracting their arinatures, these relays jointl elo:-e a circuit for the release magnet 2.12 which restores the c nnector ll to normal position in the well known manner. llelay Qtll also disconnects around from the relez se trunk conductor 15$), thus breaking" the lot-hing circuits of relays 205 and 1208. This operation also breaks the holding circuit extending back over the release trunk conductor to the line switch C, and the holding winding L2 is deenergized to permit the restoration of the line switch. At the same time relays 11(5 and 10d associated with the. answering and multiple jacks I 1 and 3*, respectively are deenergized, and the calling line is thus returned to normal condition ready to llllllit) another call, or the he 'alled. The -alled line, of course, is cleared by the release ot the connector H which removes ground from the conductor 291, thus deenergrizingr all the relay windings associated with the alled line which had been energized during: the eimversation.

llarii'ig described the process of setting up a lo ill connection, the manner in which a coni'iection is extended to the main ex change will now be described it being assumed that the i-aihscriher at substation A desires to ohlain connection with some subscr'her whose line t :n'iinates in the main exchange. ll hen the receiver is removed at substation it the same operations which were described beliore talte place and the railing: line is extended by means of the individual line switch U to an idle lotal connector, which we will assume to he the connector The main exchange trunk lines ii. are ternilnaiial in the tenth level of the lo :al rorniector and in order to obtain aceew; to these trunk lines, therefore, the ailing subscriber will have to operate his calling device in accordance with the digit 0. The connector switch responds in the manner before described and the vertical magnet QlO, under the control oi the line relay, raises the switch shattstep by step until the wipers stand opposite the tenth level of bank eoniacts. li' hen the i i-witch shaft arrives at the tenth lereh the cup spring casinc; mounted on the top oil the shaft ongages the shalt spring 22? and springs 225 and 2:27 are brought into on 'agemcnt with their working ronlarts. its i result a circult is closed a" sprin 2%?) which includes the winding of relay Elli; and the upper winding of the ring cutoll relay 205 in series. lloth lllGH relays are energized and relay 2% disconnects the exchange battery vfrom the windings oi the impedance coil Ell and connects the inner terminals of the two windings together. lillow acting series relay 2012 is energized in series with the vertical magnet and consequent y when the shalt spring 2LT ennages its working contact on the arrival of the shall at the tenth level relay 202 will be energized and a circuit will he chased for the test relay 206, which may be traced from the release trunk conductor li'il) ivy way oil spring; .227 and its working contact, armature 22]. and its workin; contact, the interrupter conact of the rotary magnet i211. and the winding of test relay you to battery. Upon energizing, rclay 1206 establishes a loijtliingr circuit for .itsell at armature B ll, and at armature 255 prepares a circuit for the rotar magnet 21.1. Atthe end of the vertical movement of the switch the slow acting relay 202 deenergizes and at armature Q21 closes a circuit tor the rotary magnet which extends from the grrourulcd release trunk conductor 159 by way of spring :22? and its working contact, armature 221 and its resting contact, armature J and its working contach armature E l-Z and its r int; contact and the winding of the rotary magnet 9,111. to battery. Upon the closure of the above circuit the rotary magnet is operated and rotates the switch shatt one step to bring; the wipers into engagement with the contact set in which the first trunk line is terminated. lllhe slow acting relay 20? is energgincd in parallel with the rotary' magnet 2i! and at armature i237 wiper 9131i. lo the circuit of connects the test lr'hen the rotary magnet the test relay E306. energizes and rotates the switch wipers into engagement with the first trunk line, it also opens its interrupter contact and ln'eaks the circuit oi the test relay and which accordingly Falls hack and at armature C235 ,ln'calcs the e'rcuit oi the rotary magnet and the circuit oil the slow acting relay Edi. The rolary Inraniet at once deenergrixes and again closes its interriu 'iter eontaeh but relay 207 being slow actine' remains in ope 'ated position for an instant and retains the test wiper now be ngclosed, if the first trunk line is.

busy the test'wiper will find a ground potential on the testcontact with which it isin engagement and, the test rela 206 will again energize, close itslockingcircuit; and againclose the circuits. of the rotary magnet 2-11 an clj the slow acting relay 207,. Therotary merit with the second contact set.

test relay 206 will continue to operate alternately in this manner as long as the test wiper 261 continues to engage busy orv grounded test contacts, relay 297 remaining in operated position meanwhile to retain the test wiper in connection with the circuit of the test relay 206. As soon as an idle trunk line isreached, which we 'will assume to be the trunk line,

shown in the drawi'ngi'aiid comprisingcond-nctors 7'1}, and 72, test wiper 261 will rind no ground potential on the test contact 270 and the test rel ay206 will fail to pull up on the last deenergization of the rotary magn'et'Qll. The rotary movement the upper winding Ofthe switching relay" 208, which may'bei'traced as follows from the grounded release trunk conductor 159 by way or armature 234 and its resting contact, upper winding of the switching relay 20 8, resting contactof armature 237 and the said armature, normally closed contact springs controlled by armature Q lO, test Wiper 261,

test contact 270, conductor 71,. armature 49.

and its resting contact, winding of relay 30, and; the winding of relay 32 to battery. Upon the closure of the above circuit relay 208 is. energized in series withrelays30' and 32 and performs the same functions in the connector H as were described in the case where a connection was extendedto the line of substation A. In, the cord circuit 0., relays 30 and "-32 are energized and the former relay at armature 4:1 disconnects the sleeve relay 35, while at armatui'es 40, and 12 the conductors 20 and 21 of the trunk line are disconnected'from the tip andring strands of the cord circuit. The energiza' tion of relay 30 thus completely separates the conductors of the trunk line'irom those of the cord circuit 0 and prevents the oper-.

exchange, will be c'utotf'from its source of 7 It will be seen'that the rotary magnet 211 and the 20 and 21 is the one taken foruse.

current, and its armature will be shifted "under the influence of the ret ractile s 'taring.

Relay 34 is not energized, however, because relay 32*, which is now energized, has disconnected ground from the polar relay armature at armature. 46. In order to notify v the branch exchange operator that the trunk line is in use, the busy'l-amp L is now lighted over 'a branch extending from the groundedconductor- 71. r

The connection to the main exchange trunk line has now established and the trunk line has been properly isolated for the sole use of the, calling subscriber. The main exchange operator is signalled automatically without further act on'the part of the calling subscriber by the operation of the line relay 15 at the"dist ant end of the trunk line." This line relay energizes in series withthe impedance coil 203v which is now connected in bridge of the connector line wipers; 260 and 2692. Upon energizing, line relay 15 lights the line lamp L, which notifies the main exchange operator that a call has been received. The operator answers by plugging into the jack J and completes the connection to. the desired local line with one of her cord circuits in the usual and" well: known, manner.

The release of the cennection is under the control of the branch exchange subscriber who by replacing his receiver can release the connector H in the same way as was, de-

scribed in the case of the local connection.

An inter-exchange connectionin reverse direction, or from, the main exchange to. the branch exchange, will now be described briefly and for'this purpose "it will beassumed that some subscriber in the mainexe. change is calling a arty at substation A in the branch exchange. At the main ex-. change the operator who handles the call will plug into" an idle trunk line extending to. the branch exchange and we will assume that-the trunk line comprising conductors The polar relay 3-3 is normally bridged across the two conductors of the trunk line at the cord circuit 6 and is energized by current flow through the windings of; the line relay change operator plugs into the jack J line relay 15 is disconnected from the trunk line, and current is supplied to the trunk line from the cord circuit. The arrangement is such that when the operator plugs, in ourrentfiow over the trunk line is reversed, as

will be understood by the partial showing of the main exchange operators cord circuit which is indicated by the reference characterO The cord circuit may be of any well known common battery type and the incomplete circuit arrangement shown is intended merely to indicate the arrangement for reversing the battery when the plug is inserted in the jack. To proceed, when the direction of current flow over the trunk line is reversed polar relay responds by shifting its armature and a circuit is completed for the slow acting relay Upon energizing. relay 3 L disconnects conductor 71 from the winding of relay 30 and connects it to ground instead. By this operation a ground potential is placed upon the test contact 270 and its multiples in the banks of the local connectors and the trunk line is made busy. At the same time the busy lamp L lighted to notify the attendant operator at the branch exchange that the trunk line is in use.

The main exchange ope 'ator will now ring over the trunk line in order to operate the relay 31, the lower winding oit which is connected across the trunk line at the cord circuit in the branch exchange. Upon energizing, relay 31 establishes a locking circuit:- lfor itself at armature latand at armature 13 closes a circuit for the call signal lamp L The lighting of this lamp signals the operator at the branch exchange. The operator answers the call by throwing the listening key K which opens the two strands of the cord circuit and connects her head set in bridge of the conductors of the trunk line. Although currentto the polar relay 83 is interupted by this operation, the armature of the polar relay remains in its shil'ted position under the influence of the retractilc spring and relay 31.- remains energized. hen the attendant operators head set is bridged across the trunk line a current flow is established which operates the supervisory relay in the main exchange operators cord circuit and extinguishcs the supervisory lamp. The main exchange operator will now respond and advise the OpOl'tlllOL in the branch exchange oi the number ot the party desired.

Having received the required information, the operator at the. branch exchange will plug into the jack at her position which is associated with the desired line. This may be the jack J. or the jack J but assuming that the jack J is the one in which the plug associated with the cord circuit 0 is inserted, upon the insertion of the plug in the jack a circuit is completed over the sleeve of the cord for the sleeve relay llpon energizing, relay 35 connects relay 36 in bridge oi. the two strands ot the cord circuit at armature 55, prepares a circuit :lor the trunk supervisory lamp L at armature 5%, and. at armature 52 closes a circuit for relay 32. Upon energizing, relay 32 opens the locking circuit of relay 31 and disconnects the lower winding of this relay from in bridge of the cord circuit, these operations being performed at armatures 4:5 and 17, respectively. In addition, relay S2 disconnects ground from the polar relay armature at armature ac, but this causes no harm for the polar relay armature is maintained grounded at armature 53 of relay 35.

Considering now the efl'eet on the line equipment of the called line, when the trunk plug is inserted in jack J a circuit is completed in an obvious manner for relay 117 which energizes and at armatures 120 and 122 disconnects conductors 110 and 112 from conductors 130 and 133 and connects them instead with the tip and ring springs of the jack J". This operation disconnects the called line from the individual line switch C. Relay 117 also connects ground to conductors 131 and 111. By the latter operation the busy lamps L and L are lighted, the latter lamp being useful in indicating to the operator at the multiple position that the line is in use. The grounding of conductor 131 energizes the cut-off winding 142 of the line switch C, resulting in the operation ot' the cut-off armature 1 17. Ground is also extended over the branch including conductor 181 to test contact: 26 1- and its multiples in the banks ol the connectors in order to make the called line busy. By the grounding oil conductor 111, relay 10 i is energized and this relay operates to disconnect relay 105. This is done in order to prevent the operator at the multiple position from listening in on the connection.

The branch operator may now restore key K to normal position, and throw key K to ringing position momentarily in order to project ringing current out over the called line. lVhen key I: is restored the trunk line is connected through to the upper and lower strands oi the cord circuit and relay 36 which is connected in bridge of the cord circuit is accordingly energized. Current flow through the winding oi. relay 36 serves to maintain the supervisory relay in the main exchange cord circuit operated and keeps the supervisory lamp extinguished while at the branch exchange the cnergization of relay 36 lights the local supervisory lamp L lVhen the called subscriber answers by removing his receiver, his transmitter is supplied with talking current from the cord circuit at the main exchange. This energizes relay 37 which is included in the upper strand oi? cord circuit 0 at the branch eX- change and disconnects relay 36 from in bridge oi the cord circuit. Upon dcencrgizing, relay 36 extinguishes the supervisory lamp L in order to notify the branch operator that the local subscriber has answered. 'll1c "con1plet"e connection has now been established and the subscribers may converse as desired. \Vhen the conversation is linished both parties will hang up their relllll resistancejrelay 33 across the line.

is reversed.

ceivers. The replacement of the receiver by the main exchange'subscriber, of course,

exchange subscriber'at substation A hangs up, relay 37 is deenergized, relay 36 is thus againconnected in bridge or" the two strands of the cordcircuit O and is operated toagain light the-local supervisory lamp and ive the branch exchan e erator a a 3 disconnect signal.

It the branch exchange operator pulls the connection down first the relay will be deener'gized andrelay 36 will be disconnected from in bridge of the cord circuit thus leaving only the high Relay 33 is in such high resistance that the supervisory relay ot the main exchange cord circuit will fall back and give the operator a disconnect signal onthe trunk end of her cord. In case the main exchange operator should pull down the connection first, line relay 15 is again connected in bridge of the trunk line and t-he current flow through the Winding of the polar relay 3'8 Relay 33 accordingly operates toshift its armature into normal position, as fsho wn in the drawing, and a circuit is completed for the trunk supervisory lamp L which is lighted to give the branch operator a trunk disconnect signal. In either case it will be seen that when .the subscribers hang up their receivers each operator gets a local disconnect signal, while the last operator to pulldownthe connection receives a trunk CllSCOllIlGCt-Slgl'ltllll addition to the.

local'disconnect signal which indicates to her' that the other operator has pulled down the connection.

- In case'the branch operator should find it necessary totalk to the local subscriber while the trunk plugis inserted in'thejack at any time, the key K may be thrown to listening position in order to bridge the op'erators head set across the tip and ring conductors of the plug. Since the operation of the listeningkey opens the two strands of the cord circuit the supply oft-alking current to the local subsciber from the main exchange will be cut oil, and retard coils 38 and 39 are provided, therefore, in order to supply talking current to the? local substation under these circumstances. It will be noted that both of the listening keys Knnd- K operate to open the conductors of the cord circuit. The circuit is arranged in this way in order, to prevent the branch operator from listening in on any c0nnectionafter the same 1s established.

operate the branch exchange as a manual system. The change from automatic to manual operation is effected by actuating a... key K4, shown in Fig. '2, which ever the self locking type and which will remain in operated position when actuated until it is manually restored to normal. This key is included in the open main conductor 162 and 1n operated position is eliective'to the connect the pull down windings of all the individual line switches, such as the line sw1tchC, from the negative pole of the branch exchange battery. Assuming that the key K is in operated position, then the process of obtaining a connection from the local SllbS'CiltlOIl A ma be consideredbrlefi NVhen the receiver is removed circuits are completed, as in the case previously de-: scribed, for the line' relay 1 10 of the individual line switch (land for the line relay 115 associated with the answering jack 3. Both relays are energized but now the energization of the line relay 1 10 is without effect for the battery is disconnected from the ull down winding 14:1 and the line switc 1 C, therefore, cannot be operated; It follows, therefore, that the line relay 115 will remain energized and will light the call "signal lamp L in order to notify the branch operator that a call has been received. On perceiving the signal, the operator willanswerthe call by inserting the answering plug of one of her local cord circuits, the cord circuit 0 for example, in the'jack J. As a result relay 117 is energized and the line conductors 101 and 102 of the calling line are connected with the tip and ring strands of the jack. Relay 117 also grounds conductors 131,181, and 111 with results which may bebriefly pointed out. By the grounding of conductor 131 the busy lamp L is lighted and the holding winding 142 of the line switch Cisenergized. This opcrates the cut-oil armaturelt'? and disconnects the line relay 1 10. By the grounding system before the connection in question is terminated. 1 By the grounding of conductor 111 the busy lamp L is li hted at the multiple position, and relay 10a is energized. The operation of relay 10 1 opens the circuit of relay 105 and prevents the operator at theinultiple position from interfering with the connection.

In. case a local connection isdesired, the calling plug of the local cord circuit in .use is inserted in the jack associated with the desired line, and the desired connection is thus completed. The local cord circuit 0 is :a well known type of cord circuit and it is so'extremely simple that it is believed to be unnecessary to go into any further details.

: Incase the local subscriber at substation A desires a trunk connection to the main exchange, the answering plugof the lo -al cord circuit will be withdrawn and the trnnlr plug associated with an idle main exchange trunk line will be substituted therefor. lhe operation of completing the conncrtimi from the local substation to the desired station in the main exchange will then take place substantially as was described in the case where a, main exchange sulscriher was calling branch exchange subscriber, except that certain of the operations take place in the reverse order. It may be stated that the branch exchange operator is able to signal the operator at the main exchange by throwing the listening key which bridges her head set across the trunk line and operates the line relay 15 at the main exchange.

Although as stated hereinbe'lore the branch exchange system shown herein is a. 100 line system, it will he understood that the size of the system may be increased to any desired extent by inserting selector switches between the individual line switches and the local connectors accordiin); to well known practice. T

If the size oi the system is thus increased to a considerable extent: it will make it necessary to use several multiple positions in addition to the usual answering) position, and it is chiefly on this account that the circuit arrangements for wiriim the multiple positions have been shown in l ie. 2. It should he understood, however. that under certain circumstances a multiple posi tion may be used even in a 100 line a for the conditions under which the s operating may be such as to require two switchboards which are located at ('lllliQlOlilT points, all of the subscribers lines being multipled in both switch-boards.

Attention is directed also to an ad vantage which is secured by the 11 art1icular scheme employed tor changing the system 'l'rom automatic to manual oi eration. llnasnuuh as the lcey which is used tor this purpose acconu'ilishes the desired object by opening, the open main conductor, it will be seen that whenever this conductor is opened by the master switch in the ordinary operation of the system as an automatic 5 tom. as when all the outgoing trunk lines are busy. the system will for the time being he changed automatically to a manual s'y tom independent of the actuation of the hey. in other words, it a subscriber makes a call when all the local connectors are busy. he will sinnal the operator. while it any connector available it will he talren for use and the operator will not he signalled.

Having described my invention. what; I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

What I claim as my invention is:

1. In a combined automatic and manual telephone system. subscriber controlled automaic switches for connecting calling and called lines, operators manual equipment for connecting calling; and called lines, and operator controlled means for causing the system to operate as an automatic system or as a manual system at will.

In a combined automatic and manual telephone system. subscriber controlled automatic switches for connecting calling and called lines. operators manual equipment for connecting calling and called lines, and a centrally loci ted device operable at will to cause. the system to operate as an automatic system. or as a manual system.

3. la a combined automatic and manual telephoi'ie system. subscriber controlled automatic switches for connecting calling and called lines operators manual equipment tor connecting callin and called lines, and a key at an operators position for determinin whether the system is to operate automatically or manually.

-l. in a tclepl'ione system, subscribers lines, subscriber controlled automatic switches for coimecting; calling and called lines, operators manual equipment for connecting calling and called lines, the automatic equipment being; normally operative responsive to calls and the manual. equipment being normally inoperative, operator controlled means for rendering the automatic equipment inoperative, and circuit arrangements such that the manual equiynnent is automatically rendered operative when the automatic equipment is rendered inoperative.

5. In a. telephone system, a subscribefls line and a manual jack individual thereto, an automatic switch for extending said line when calling, a signal, associated with said jack. means for operating said signal responsire to a call. means for preventing the operation of said signal when said switch is operated responsive to a call, and means for preventing: the operation oil said switch responsive to a call in order to permit said signal to be operated.

6. in a telephone system, a subscribers line, a manual jack and an automatic switch imflividual to said line, a cut-olii relay for disconnecting the operating and connecting elements of the switch from the line when the operator plugs into said jack, and a second cut-oli' relay controller'l by said switch for disconnectiiug the said first cut-otl:' relay.

T. In a telephone system, a subscribers line. a manual jack and an automatic switch individual to said line. said jack being normally disconnected and the said switch being: lun'mally connected, a line relay and a cut-oil" relay for said switch, a second out oil relay for'diseonnecting the switch and its line relay and for connecting the jack when the operator plugs into the jack, and another relay controlled by said switch for disconnecting the said second cut-oft relay.

8. In a telephone system, a subscribers line, a manual jack and an automatic switch individual to said line, the tip and ring springsof said 'jack being normally disconnected, and the corresponding contact elements of the said switch being normally connected, a relay for disconnecting the switch contact elements and for connecting the springs of said jack when the operator plugs into the'jack,and means for preventing the operation of said relay in case the said switch is operated before the operator plugs in. i

flines a manual answering ack for each line,

a 9 In a telephone system, a subscribers line, a manual call signal and an automatic swit-ch individual to sa1d line, two line relays individual to said line, one controlling said signal and the other controlling sa1d switch and both normally responsive to calls,

and means controlled by the line relay which controls the said switch for disconnecting the other line relay.' r p I :10, In a telephone system, subscribers lines,a manualanswering jack foreach line,

trunk lines, automatic switches for extending calling lines to idle trunk lines, means operated by, acalling subscriber for signalling the operator in case allot said trunk lines are busy, and meansresponsive to the seizure of an idle trunk for rendering said signalling means ineffective.v I I "11, In .a {telephone :system, subscribers trunk lines,.automatic switches :for extending calling lines to idle trunk lines, means operated by a calling subscriber for signalling the operator, in caseall of said trunk lines :are busy, and means responsive to the seizure of an idle trunk for preventing a calling'subscrlber from slgnallmg the operator in -case an idletrunk line is available.

12. In a telephone system, subscribers lines, a manualjack and an automatlc r0- .tary trunk selecting switch. lIlCllvldllal to each line, agroup oftrunk lines accessible tosaid switches, allinesignal for each jack, and circuit arrangements whereby a callmg subscriber will operate his jline switch to ICOH- nect with an idle trunk line if idle trunks are available and will 0 crate the associated line signal in case allo said trunk lines are busy; I

13. Y a telephone system, subscribers lines, manual jacks for said lines, operators cord circuits 'for connecting calling and called lines "through the associated jacks, subscriber controlled automatic switches for connecting calling and called. lines, and

means for preventing an operator from connecting with anyline when the same is busy either in an automatically; established connection or in amanually established connec-' tion.

:14, telephone system, subscribers lines,manual jacks for said lines, operators cord circuits for connecting calling and called lines through the associated jacks, subscriber controlled automatic-switches for connecting calling and called 7 lines, and means for preventing an operator from connecting with any line when the same is busy either as a calling or as a called line in 7 ity ofoperators positions, and means individual to said line effective whenever an operator plugs intoany one of said jacks, for preventingother operators from listening in on the line by way of another one of said jacks.

line, multiple jacks for said line at a plurahty of operators positions, each jack being ,normallyrdisconnected from the line,

17. In a telephone system, a subscribers means for connecting any jack with the line when an operator plugsin, and means'for thereafter preventing anotheroperator from" connecting another jack with said'line by plugging into such other jack.

I 18. In a telephone-system, a plurality of vtelephone lines equipped 'with automatic substations, subscriber controlled automatic switchesfor connecting said lines, operators manual equipment fqr; connecting saidlines, andmeans comprisiuga switchin the battery'feed conductor for certain of said'automatic switches forcausing the system to operate automatically or manually I as desired. r v I i 19. In a telephone system, a plurality of telephone 1 lines equipped; 'with automatic substations, subscriber controlled automatic switches for connecting said lines, operators 'manual equipmentifor connecting said lines, I circuit arrangements such that the system is normally operative automat cally, there'being means controlled by certain vof the switches for rendering the system inoperative manually, and means for renderingthe said last mentioned switches inoperative to permit the systemt'o operate manually. 20.; In a telephone system, a-plurality of telephone lines equipped with automatic substations, subscriber controlled automatic switches for connecting said lines, operators I manual equipment for connecting said lines, and asingle operator controlled switch a t-.

Feeling; all the said lines simultanc uslr l'or uteautou'iat ically or unuiually.

it. in a telcpl'ione syst in. a pin ulity of telephone lines equipped with automatic substations, subscriber controlled automatic switches for connecting: said lines perator's manual equipment 't'or connecting said lines. and manually operable means consisting? solely oi elt-uneuts conunou. to said lines for tletern'iinine Whether the sys-itcin is to operate automatically or manually.

22. Tu a telephoni- .iltll'l. a subscriberline, a manual jack and an automatic switch individual to said line. a cut-oil relay includii'in" an armature and contact springs actuated thereby ior dinconuectingr the line. from the talkine; coiulucttn's extending: to the switch when the operator plur's into said jack, and a second cut-oil relay coi'itrolled by said switch for diw-onnectiiur the said first cut-oil relay.

28. In a telephone system. a suliaciiliiefis line, a manual. jack and an automatic switch individual to said line. said incl: hcingr normally disconnected and the said switch being: normally connected, a line relay and a cut-oil relay for said switch, a second cutwotl relay for disconnecting; the switch and its line relay and for connecting: the jacr when the operator plugs into the jack. and another relay controlled by said switch tor disconnecting: the said second cut-oil relay.

2%. In a telephone system. a sn seriliers line, a call signal and an automatic switch individual to sa d line, a pair of line relays individual to said line, one eontrollin said signal and the other controlliinr said iioritch, means for sinniltaneously operating both o't said line relays. and means controlled hy the line relay which controls the said switch for disconnection; the other line relay.

In a telephone system. a. suhscrihefs line, amanual jack and an automatic switch individual to said line. a. cut-oil relay for (,lisconnccting the switch when the operator plugs into said jack, a second cut-oil relay controlled by said switch tor discoiniectingg the said first cuboil' relay. :1 third cut-ell relay for performing functions similar to said first cutcil relay. and a fourth cutotl relay controlled by said first eutotli' relay for disconnecting); the said third cut-otl' relay.

26. In a. telephone system. a subscrihers line, two jacks in diridu al to said line, a relay associated with each jack for connectinnthe same to the line. a second relay associated with each jack for opening); the circuitol the associated connecting relay, and a circuit for each of said second relays controlled by the non-associated connect-inn; relay.

.27. In a telephone system, two exchanges, means including a trunk line and manual connective. equipment at each end thereof for handling calls from the first exchange eanna to the second exchange, means includhu}: said trunk line. the manual connective equipment at the iirst exchange. and subscriber controlled switches at the second exchange for handling); calls from the second exchange to the first exchange. and means effect ve whenever the trunk line is in use in a. call oi the second n'lcntioned class for discoi'inectingr the manual connective ciplipiuent in the sec mid cxchaiure from the trunk line.

525?. in a telephone system. two exchanges, means inchuline a trunk line and manual connectirc equipment at each end thereof for handling); calls from the first exchange to the second mzchangre, means including said trunk line. the manual connective equipment at the first. crurlnrnoe and suln criber controlled sn chen t he second exchange tor haniii-u calls from the second exchange to the exchange, an operators listening key incl uded in said connective equipment at the. second exchange, and means effective whenever the said trunk line is in use in a call of the second mentioned class for opening the trunk conductors at a point between the oing); section. of the trunk and said key so as to prevent. the operator from listening.

529. In a telephone system, a jack in one exchange, a plug" ending cord circuit in a second exchange, a. trunk line extending; troni said jack to said cord circuit, a sleeve relay in said cord circuit energized when the plan; is inserted in the jack of it called line, a polar relay bridged across said cord circuit and controlled by a reversal of current llow over said trunk, and a supervisory lamp associated with said cord circuit and controlled by said two relays jointly.

1:30. In a telephone system, a jack in one exchange, a. plug; ending cord circuit in a second exchange, a trunk line extending from said jack to said cord circuit means includiiur said jack, trunk line, and cord circuit; for connecting a. calling line in the iirst exchange will. :1 called line in the second PTH'lHIlhQK means in the first; exchange tor supplying; talking current. to the called line over said trunk line, an operators listeninn; key in said cord circuit arranged to open the talkin strai'ids thcreoil' and connect the tilltl'tllfil r't head-set to the. section associated with the called line, and means in said cord circuit connected up by the operation of said her to:- supplying); talking, current to the called line while the key is in actuated position.

ill. in a telephone system, a jack in one cvwluuure. a plug: ending; cord circuit; in a second exchange. a. trunk lino extending tron] said jack to said cord circuit, means including said jack, trunk line, and cord circuit tor connecting av calling line in the first exchange with a called line in the second exchange, means in the first exchange :tcr supplying talking current to the called line over said trunk line, two listening keys at said cord circuitfor enabling the operator to talk to the calling and called parties, respectively,'each key being arranged to open the talking strandsof the cord circuit to re strict the talking circuit to the operator and the wanted party, and means associated with i the'key used to talk to the called party for supplying such party with talking current from the second exchang 32. In a telephone system, a jack in one exchange, a plug ending cord circuit in a sec- I ond'exchange, a trunk line extending from said jack tosaid cord circuit, means including said ack, trunk line, and cord circuit for connectlng a calling line in the first exchange with a called line'in the second exchange, means in the first exchange for supplying talking current to the called line over said trunk line, a bridge at said cord circuit closed responsive to the insertion of the cord circuitplug in the jack of the called line to draw current from the talking current supply at the first exchange, for maintaining supervisory conditions at the first exchange,

CLARENCE E. LOMAX. 

